We have previously identified regions of human interferon-gamma (IFN- gamma) genomic DNA which can enhance gene expression in murine and human cells after linkage to a heterologous gene. One enhancer region of DNA lies in the 5' non-coding region of the gene, appears to be cell specific and is inducible by phorbol esters. The second enhancer region lies in the first intron, is not tissue specific, and is stimulated by PMA in T cells. These results indicate that control of IFN-gamma gene expression involves multiple DNA regions and that the role of these enhancer elements in gene expression may depend upon the signal transduction pathway utilized. We are now identifying the DNA binding proteins which interact with the IFN-gamma genomic DNA and comparing the levels of these proteins in purified lymphocyte subsets. These studies will enable us to determine if the extra cellular signaling which results in IFN-gamma gene expression correlates with a modulation in the levels of specific DNA binding proteins.